Online Trick

Apprentice Piece with Lattice Graphs

Lattice graphs can be quite tedious to learn. I don't use them too often and  when I need them I usually have to dig deep into the archives for details on the parameter details.
The here presented example may serve as a welcome template for the usage of panel functions, panel ordering, for drawing of lattice keys, etc.
You can download the example data HERE.

(Also, check this resource with examples by the lattice-author). 

library(lattice)
df <- read.csv("PATH/TO/Downloads/lattice_data.csv",
               header = T, sep = ";")
mypch <- rep(21, 3)
mycol <- c(rgb(0.2, 0.8, 0.9), rgb(0.8, 0.2, 0.9), rgb(0.9, 0.2, 0.2))

stripplot(mean ~ group1 | item_parc, groups = group2, data = df,
          type = c("a", "p"), strip = strip.custom(strip.names = c(F, T)),
          ylab = "Score-Mittelwert", layout = c(2, 4),
          scales = list(y = list(cex = 0.9),
                        x = list(cex = 1.1, labels = c("männl.", "weibl."),
                        tck = c(1, 0))),
          par.strip.text = list(cex = 0.9),
          panel = function(...) {
             panel.stripplot(..., col = mycol, pch = mypch, fill = mycol)
          },
          index.cond = list(c(7,8,5,6,3,4,1,2)),
          key = list(space = "bottom", text = list(c("Alter < 35 J.",
                                                     "Alter 35-50 J.",
                                                     "Alter > 50 J.")),
                     points = list(col = mycol, cex = 0.8, pch = mypch, fill = mycol),
                     rep = F))